The present invention relates to microfabrication of semiconductor devices, and, more specifically, to structures and fabrication methods of thermoresistance sensors.
Precise, local measurement of temperature in an integrated circuit (IC) is typically viewed as an important factor in IC operation. Traditional solutions employ junction bandgap references in, for example, diodes and/or bipolar junction transistors (BJTs) to measure temperature. However, these may require extensive calibration to achieve a one degree Celsius resolution. In addition, silicon-on-insulator (SOI) lateral diodes and/or BJTs can be expensive to engineer. Because lateral diodes use 1D junctions, they require a relatively large area, and BJTs are difficult to manufacture since source/drain formation is now typically done in-situ with epitaxial growth techniques. Further, vertical BJTs are generally not available in SOI, and, in the manufacture of finFETs, a lower volume of silicon is typically available, which can increase difficulty in forming a suitable bandgap. Fin-based technologies pose a challenge when making planar devices, such as due to chemical mechanical polishing (CMP) and/or point of contact/connection (POC) issues.
An option that can be relatively easily and inexpensively included in most semiconductor manufacturing techniques is to employ high precision, thermally sensitive resistors. However, front-end silicon-based resistors typically have low sensitivity because other components are also responsive to temperature variations. As a result, thermal spreads can be large, which can swamp thermoresistance effects. In addition, back-end metal-based resistors are often isolated and/or far from dies, and so are affected by the overall temperature of the chip with which it is associated. Further, back-end metal-based resistors can be difficult to calibrate.